Hi nick. Welcome 
First thing i want to comment on is your stock list.
1. The Kenyi, Red Zebra and Bumblebee are possibly the 3 most aggresive mbuna you can keep. This agression is what is killing your plecos whenever you add them.
2. Mbuna prefer to be kept in harems or groups. A male/female ratio of 1M/4F works well and helps to spread agression and even reduce is a little.
3. Acei prefer being kept in harems of atleast 5 and don't really thrive in anything less.
It is possible to keep a couple of pleco in with even the most agressive mbuna as long as you have the ratio and the tank size to support your fish.
The bumblebees and the Kenyi both need larger tanks then the one you have, so i would remove them straight away. I would even consider removing the red zebra because they grow large, get very agressive and hybridise with other fish very easily especially in smaller tanks.
I would then add to your current stock list:
2 more cobalts (1m/4f)
2 more female johanni
3 more Acei
4 more rusties (1m/4f)
That would be a total of 20 fish not including the cats or laoches which i wouldn't add to.
Your agression will drop dramaticly and it will be safer to add a pleco.
Mbuna are very agressive so it is important to house compatible fish and suitable fish for a better chance of success.
Good luck :thumb:
First thing i want to comment on is your stock list.
1. The Kenyi, Red Zebra and Bumblebee are possibly the 3 most aggresive mbuna you can keep. This agression is what is killing your plecos whenever you add them.
2. Mbuna prefer to be kept in harems or groups. A male/female ratio of 1M/4F works well and helps to spread agression and even reduce is a little.
3. Acei prefer being kept in harems of atleast 5 and don't really thrive in anything less.
It is possible to keep a couple of pleco in with even the most agressive mbuna as long as you have the ratio and the tank size to support your fish.
The bumblebees and the Kenyi both need larger tanks then the one you have, so i would remove them straight away. I would even consider removing the red zebra because they grow large, get very agressive and hybridise with other fish very easily especially in smaller tanks.
I would then add to your current stock list:
2 more cobalts (1m/4f)
2 more female johanni
3 more Acei
4 more rusties (1m/4f)
That would be a total of 20 fish not including the cats or laoches which i wouldn't add to.
Your agression will drop dramaticly and it will be safer to add a pleco.
Mbuna are very agressive so it is important to house compatible fish and suitable fish for a better chance of success.
Good luck :thumb: